Optional coolant return from heater core. Not all radiators have the heater return option. My '70 doesn't.View attachment 413095
I need to hook up heater hose. The 2 nipples on the pic get connected, water pump to intake. I think I need to come out of the intake at the black plug and go to the heater core. Then out of the heater core into the radiator port. What's the black plug in the water pump for?